ElAM: A computer program for the analysis and representation of anisotropic elastic properties

Copyright © 2010 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Computer Physics Communications. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Computer Physics Communications, Volume 181, Issue 12 (2010), DOI: 10.1016/j.cpc.2010.08.033The continuum theory of elasticity has been used for more than a century and has applications in many fields of science and engineering. It is very robust, well understood and mathematically elegant. In the isotropic case elastic properties are easily represented, but for non-isotropic materials, even in the simple cubic symmetry, it can be difficult to visualise how properties such as Young's modulus or Poisson's ratio vary with stress/strain orientation. The ElAM (Elastic Anisotropy Measures) code carries out the required tensorial operations (inversion, rotation, diagonalisation) and creates 3D models of an elastic property's anisotropy. It can also produce 2D cuts in any given plane, compute averages following diverse schemes and query a database of elastic constants to support meta-analyses. Program summary Program title: ElAM1.0 Catalogue identifier: AEHB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEHB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 43 848 No. of bytes in distributed program, including test data, etc.: 2 498 882 Distribution format: tar.gz Programming language: Fortran90 Computer: Any Operating system: Linux, Windows (XP, Vista) RAM: Depends chiefly on the size of the arrays representing elastic properties in 3D Classification: 7.7 Nature of problem: Representation of elastic moduli and ratios, and of wave velocities, in 3D; automatic discovery of unusual elastic properties. Solution method: Stiffness matrix (6×6)(6×6) inversion and conversion to compliance tensor (3×3×3×3)(3×3×3×3), tensor rotation, dynamic matrix diagonalisation, simple optimisation, postscript and VRML output preparation. Running time: Dependent on angular accuracy and size of elastic constant database (from a few seconds to a few hours). The tests provided take from a few seconds for test0 to approximately 1 hour for test4

Brillouin scattering study on the single-crystal elastic properties of natrolite and analcime zeolites

Copyright © 2005 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Applied Physics 98 (2005) and may be found at http://link.aip.org/link/?jap/98/053508The Brillouin light-scattering technique was used to investigate the single-crystal elastic properties of two aluminosilicate zeolites, natrolite (NAT) and analcime (ANA), at ambient conditions. An inversion of the acoustic velocity data results in the full set of elastic stiffness moduli (Cij's) for both materials. From the single-crystal moduli the aggregate adiabatic bulk moduli (Ks), shear moduli (G), and Poisson's ratios (v) were found to be Ks=48.5(1.0) GPa, G=31.6(1.0) GPa, and v =0.232(5) for NAT, and Ks=59.8(1.2) GPa, G=32.1(1.0) GPa, and v=0.272(5) for ANA (Voigt-Reuss-Hill averages). The bulk and shear moduli of both zeolites are relatively low compared with those of densely packed aluminosilicates, reflecting an open framework structure of (Al,SiO4) tetrahedra which is easily deformed by bending the Si–O–Al angles. As expected for a less dense crystal, NAT is softer and more compressible than ANA. An evaluation of the directional Young's moduli shows that the compressibility of NAT is nearly uniform along the [100] and [010] axes, while [001] is stiffer, in agreement with previous compression studies. We do not find experimental evidence of negative Poisson's ratios for NAT zeolites as predicted by recent theoretical calculations

Single-crystal elastic constants of the zeolite analcime measured by inelastic X-ray scattering

The single-crystal elastic moduli of the zeolite analcime, vertical bar Na-16(+)(H2O)(16)vertical bar[Al16Si32O96] (structure type ANA), have been determined by inelastic X-ray scattering (IXS). The room temperature values (GPa) are C-11=103.5 +/- 5, C-44 = 30.3 +/- 2, C-12 = 21.7 +/- 2. The results demonstrate the applicability of this technique for measuring elastic constants of open three-dimensional structures that include extra-framework species. (C) 2009 Elsevier B. V. All rights reserved

Off-axis elastic properties and the effect of extraframework species on structural flexibility of the NAT-type zeolites: simulations of structure and elastic properties

Simulations of the atomic structure and elastic constants of five zeolites with the NAT-type structure, namely, natrolite, mesolite, scolecite, metanatrolite, and ammonium-exchanged natrolite, using the CVFF force field implemented within Cerius(2), are presented. The validity of the simulation method is shown by the excellent agreement between simulated and experimental crystal data, including location of extraframework ions and water molecules, and for natrolite, the only zeolite studied here for which experimental studies of elasticity have been reported, the good agreement between the simulated and experimental elastic constants. For all materials, an off-axis analysis of the elastic constants reveals that the Poisson's ratios nu(xy) and nu(yx) become negative when stress is applied at 45 degrees to the crystallographic axes. Further simulations of the elastic behavior of the materials under stress, using the molecular dynamics method of Parrinello and Rahman, reveal that the elastic behavior may be described by a "modified rotating squares" model. Here three-dimensional structural distortions are reduced to a two-dimensional model where square cross-section units of structure both rotate about their hinges and undergo change of dimension: the balance of these competing processes dictates the resulting Poisson's ratio and is highly dependent upon the direction along which stress is applied. We discuss the effect that various concentrations of extraframework cations and water have on the elastic properties of the NAT-type zeolites

An analytical model for producing negative poisson's ratios and its application in explaining off axis elastic properties of the NAT-type zeolites

A two-dimensional model involving rotation and distortion of corner-linked parallelogram units is presented and investigated as a means of producing negative Poisson's ratios. It is then shown how the model can represent the behaviour of certain zeolite materials: by introducing structural parameters from the crystal structures of five zeolites with the NAT-type structure, it is shown that the model replicates their elastic behaviour well and depends on a balance between the rotation of the parallelogram units and their distortion (by change of edge lengths and internal angle), which is dictated by the direction of applied stress. In the case of one of the materials, natrolite, the predicted values of Poisson's ratios agree well with those derived from experiment, and it is suggested that the model might be used to search for negative Poisson's ratios in other inorganic structures

Synthesis of novel magnetic iron metal-silica (Fe-SBA-15) and magnetite-silica (Fe3O4-SBA-15) nanocomposites with a high iron content using temperature-programed reduction

Magnetic iron metal-silica and magnetite-silica nanocomposites have been prepared via temperature-programed reduction (TPR) of an iron oxide-SBA-15 (SBA:Santa Barbara Amorphous) composite. TPR of the starting SBA-15 supported Fe2O3 generated Fe3O4 and FeO as stepwise intermediates in the ultimate formation of Fe-SBA-15. The composite materials have been characterized by means of x-ray diffraction, high resolution transmission electron microscopy and SQUID (superconducting quantum interference device) magnetometry. The Fe oxide and metal components form a core, as nanoscale particles, that is entrapped in the SBA-15 pore network. Fe3O4-SBA-15 and Fe-SBA-15 exhibited superparamagnetic properties with a total magnetization value of 17 emu g(-1). The magnetite-silica composite (at an Fe3O4 loading of 30% w/w) delivered a magnetization that exceeded values reported in the literature or obtained with commercial samples. Due to the high pore volume of the mesoporous template, the magnetite content can be increased to 83% w/w with a further enhancement of magnetization

The bulk material dissolution method with small amines for the synthesis of large crystals of the siliceous zeolites ZSM-22 and ZSM-48

The hydrothermal reaction between silica glass and aqueous solutions of amines and sodium hydroxide has been investigated for the preparation of large crystals of siliceous zeolites. In the presence of n-butyl-amine at 160 degrees C needle-shaped crystals of ZSM-22 (TON-type) are formed. By adjusting the amount of n-butylamine used in crystallisation, crystals of up to 400 mu m in length may be formed after 5 weeks of reaction. Calcination in air at 800 degrees C produces crystals free of template and scanning electron microscopy shows the samples to be free of cracks, with no evidence of loss of integrity of the specimens. The quality and indentity of the ZSM-22 crystals, both before and after calcination, is verified by using single crystal X-ray diffraction and Si-29 MAS NMR and the refined structures compared to those previously reported for the same material. If the amine used in synthesis is 1,6-diaminohexane, usually used to prepare TON-type zeolites, then samples of ZSM-48, a disordered zeolite, are produced. These have very different crystal morphology, the samples being made up of intergrown plate-shaped crystallites agglomerated into spherical objects. The results we present illustrate the scope for the general use of the 'bulk material dissolution' method in the synthesis of siliceous zeolites as large single crystals. (C) 2008 Elsevier Inc. All rights reserved

Novel magnetite-silica nanocomposite (Fe<SUB>3</SUB>O<SUB>4</SUB>-SBA-15) particles for DNA binding and gene delivery aided by a magnet array

Novel magnetite-silica nanocomposite particles were prepared using SBA-15 nanoporous silica as template. Magnetite nanoparticles were impregnated into the nanopore array of the silica template through thermal decomposition of iron(III) acetylacetonate, Fe(AcAc)(3) at 200 degrees C. These composite particles were characterized using TEM, XRD and SQUID magnetometry. The TEM images showed that the size of composite particles was around 500 nm and the particles retained the nanoporous array of SBA-15. The formation of magnetite nanoparticles was confirmed by the powder XRD study. These composite particles also exhibited ferrimagnetic properties. By coating with short chain polyethyleneimine (PEI), these particles are capable of binding DNA molecules for gene delivery and transfection. With an external magnetic field, the transfection efficiency was shown to have an increase of around 15%. The results indicated that these composite nanoparticles may be further developed as a new tool for nanomagnetic gene transfection

Negative Poisson's ratios in siliceous zeolite MFI-silicalite

Brillouin scattering measurements of the single-crystal elastic properties of the as-made zeolite silicalite vertical bar(C3H7)(4)NF vertical bar(4)[Si96O192]-MFI provides the first experimental evidence for on-axis negative Poisson's ratios (auxeticity) in a synthetic zeolite structure. MFI laterally contracts when compressed and laterally expands when stretched along x(1) and x(2) directions in the (001) plane (nu(12)=-0.061, nu(21)=-0.051). The aggregate Poisson's ratio of MFI, although positive, has an anomalously low value nu=0.175(3) compared to other silicate materials. These results suggest that the template-free MFI-silicalite [Si96O192] might have potential applications as tunable sieve where molecular discriminating characteristics are adjusted by application of stress along specific axes. (C) 2008 American Institute of Physics